Automatically Activate Microphone when switching Servers is enabled, you can overwrite the server where the microphone is active by clicking on the red microphone icon for the corresponding server in the activity area.
Let’s say you have server A in the foreground where the microphone is active and you are also connected to server B.
If you are explicitly muted on server B the context menu has the option
Unmute Microphone. This will unmute and activate the microphone, which is imo expected.
If you are however not muted on server B but only have the microphone disabled you get the option
Mute Microphone. This will explicitly mute the microphone, which is also expected.
In this case, I would really like to see an explicit
Activate Microphone option.
This could also help new users, like @Obbi, to understand that this is even an option. :)